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269
Two-Stage Horizontal Bone Grafting with the Modified Shell Technique for Subsequent Implant Placement: A Case Series
Michael Stimmelmayr, Priv Doz Dr Med Dent1 Wolfgang Gernet, Prof Dr Med Dent Dr hc, PhD2 Daniel Edelhoff, Prof Dr Med Dent, PhD2 Jan-Frederik Güth, Dr Med Dent3 Arndt Happe, Priv Doz Dr Med Dent4 Florian Beuer, Priv Doz Dr Med Dent, PhD2 This case series evaluated the graft stability and resorption of a modified shell technique for horizontal ridge augmentation. Autogenous bone shells of 1-mm thickness were fixed with microtitanium screws with the gaps between the shells and ridge filled with autogenous bone chips. In 22 patients, 30 cases were performed to augment 50 regions. Forty-two implants were inserted after a healing period of 5.5 (± 1.0) months. Preoperatively, the mean width of the crest was 2.7 mm (± 0.9), after bone grafting, 6.7 mm (± 0.8), and during implant placement, 5.9 mm (±0.7), and the mean resorption was 0.8 mm (± 0.5) (P < .001). This technique showed promising results. However, due to slight resorption, the ridge should be over contoured. (Int J Periodontics Restorative Dent 2014;34:269–276. doi: 10.11607/prd.1374)
Assistant Professor, Department of Prosthodontics, University of Munich, Munich, Germany, and Private Practice, Cham, Germany. 2Tenured Professor, Department of Prosthodontics, University of Munich, Munich, Germany. 3Assistant Professor, Department of Prosthodontics, University of Munich, Munich, Germany. 4Assistant Professor, Department of Oral and Maxillofacial Plastic Surgery and Implantology, University of Cologne, Cologne, Germany. 1
Correspondence to: Dr Michael Stimmelmayr, Josef-Heilingbrunnerstr.2, 93413 Cham, Germany; fax: 09971 843588; email: [email protected]. ©2014 by Quintessence Publishing Co Inc.
While an inadequate horizontal bone width of the alveolar crest was an absolute contraindication for implant placement in the late 1980s,1 guided bone regeneration substantially expanded the range of indications for dental implants in the early 1990s.2,3 Initially, tenting screws and membranes were used to provide space for regeneration4; however, bone substitutes or bone grafts showed better clinical results.5 Small horizontal defects can be reconstructed very predictably with these techniques.6 However, the predictability of the technique decreases when the size of the defect increases.7–9 It has been shown that there is a critical size for bone defects where they cannot be reconstructed with bone substitutes.10 Hence, reconstruction of such defects increases the need for augmentation with autogenous bone grafts.11–13 But additional bone grafting at reentry is often required.12,14 In the past, autogenous bone of the iliac crest was taken for major horizontal and vertical augmentation procedures. Due to the higher resorption and morbidity
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270 of the donor site, today intraoral donor sites are more popular.15,16 Current concepts involve intraoral bone harvesting from the chin or the retromolar region. Pikos described the inlay technique, which involves placing cortical block grafts to accurately fit the residual alveolar bone.17 However, the mandibular cortical block graft needs a long period of time to become vascularised and remodeled and can be sequestrated years after the augmentation procedure.18 Khoury and Khoury described the shell technique for three-dimensional hard tissue grafting.18,19 This technique uses thin cortical bone shells to reconstruct the buccal plate and provide a space for particulated autogenous bone grafts. In this concept, the thinned cortical bone shells serve as a natural barrier membrane that maintains space and prevents soft tissue ingrowth. Harvesting these bone shells and extraoral trimming with the cutting wheel, as originally described, is very technique sensitive.18,19 Therefore, this technique was simplified by thinning out the corticocancellous bone grafts with a bone mill to create the bone shells.20 This technique was used in this study. It was hypothesized that the horizontal hard tissue augmentation of the alveolar ridge with the modified shell technique and autogenous bone will present a predictable outcome after healing, with moderate resorption and a bone volume that allows for restorativedriven implant placement.
Method and materials The requirements of the Helsinki Declaration were observed, and all patients gave informed consent for the surgical procedures. Patients that presented in the private practice of the corresponding author with partial tooth loss and a demand for rehabilitation with implant-supported fixed dental prostheses were consecutively enrolled in the study. In addition, the horizontal resorption of the alveolar crest at the planned implant position caused a two-stage procedure of hard tissue augmentation and implant placement. The appropriate restorative-driven implant position was determined by a wax-up that was transferred into a surgical guide. The exact implant position was clearly defined by a radio-opaque titanium tube (CT-Tube, Camlog) preaugmentation procedure. Implant planning was followed by a panoramic radiograph (Gendex OrthOralix 9200) and bone mapping using the planning model to evaluate the available host bone. The two-stage procedure was preferred when the position of the implant was outside the contour of the alveolar crest or if primary stability of the implant was not expected. All patients were instructed to take antibiotics (amoxicillin, 1,000 mg or clindamycin, 300 mg, 3 pills), ibuprofen 400 mg, and 50 mg prednisolon (Decortin, Merck-Pharma) to prevent inflammation and swelling 1 hour before ridge augmentation. Ibuprofen was continued for 3 days and the
antibiotics for 6 days postaugmentation. Immediately before surgery, the patients were asked to rinse their mouths with a 0.2% chlorhexidine solution for 3 minutes. A palatal shifted crestal incision in the maxilla or a central crestal incision in the mandible was followed by a sulcular incision at the adjacent tooth with only one distal relieving incision. A full-thickness flap was elevated, and all connective or granulation tissue was debrided from the alveolar crest with a curette (Fig 1). For a tension-free wound closure, the periosteum was slit basal of the flap at the beginning of the surgery to minimize bleeding during placement of the bone graft or membrane. Intraoperatively, the width of the alveolar crest was measured with a caliper (Züricher Modell, Seitz & Haag) at the central position of the planned implant as indicated by the positioning guide. The bony defect was measured with a periodontal probe (PCPNC North Carolina, Stoma) to determine the size of the bone shells. The bone graft was harvested at the oblique line in the retromolar region using an ultrasonic knife (Piezosurgery, Mectron). A corticocancellous block-graft of approximately 3-mm thickness was obtained (Figs 2 to 4). The use of an ultrasonic device seems to be more time consuming in comparison with the use of a fissure bur or diamond disk, but the technique is reported to be very safe and atraumatic. The donor site was filled with a collagen fleece (Resorba) and sutured with a row of single sutures
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271
HW pre-op
Fig 1 Severe horizontal bony defect. (HW pre-op = horizontal width of the alveolar crest before horizontal augmentation).
Figs 2 and 3 Bone block harvesting from the retromolar region with an ultrasonic device.
Fig 4 Bone block of 3-mm thickness harvested from the retromolar area.
Fig 5 Bone block placed in the bone mill during the milling process.
Fig 6 Bone block of 1-mm thickness after the milling process.
(Supramid 5-0, Stoma). The block was reduced to a thickness of approximately 1 mm with a bone mill (Bull Bone Mill, Mondeal) (Figs 5 and 6). The advantage of using the bone mill in comparison to a Luer forceps is the consistent abrasion of the bone block, leading to a smooth concave surface of the bone shells. These bone shells were trimmed and adjusted with a round bur and anchored in the host bone with titanium micro screws (Q-Bone-Grafting Set, Trinon) (Figs 7 and 10). The gap between the
shells and the alveolar bone was filled with milled bone chips obtained by thinning the corticocancellous block. Autogenous blood, taken from a vein of the left arm, was added to the graft (Figs 8 and 11). Immediately after the augmentation procedure, the width of the alveolar crest was measured with a caliper at the central position of the planned implant and recorded. The bone graft was covered with a resorbable collagen membrane (Bio-Gide, Geistlich), and the wound was closed with a combination of
deep horizontal mattress (Gore-Tex 6-0, WL Gore) and interrupted sutures (Trofilene 6-0, Stoma). The single sutures on the retromolar donor site and on the grafted site were removed on day 10, the mattress sutures on day 14 after surgery. Attention was meticulously paid to avoid any pressure from the removable dental prostheses (RDPs) on the graft during the healing period. The implants were placed after a mean healing period of 5.5 (± 1.0) months after augmentation.
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272
HW postaug HW pre-impl
Fig 7 Bone shells fixed at the buccal alveolar crest with titanium microscrews.
Fig 8 Grafting of the bony defect between the shells and the alveolar crest with autogenous bone chips mixed with blood (HW postaug = horizontal width of the alveolar crest just after horizontal augmentation).
Fig 9 Reentry and implant placement 5 months postaugmentation with good integration of the bone graft and reconstruction of the alveolar crest (HW pre-impl = horizontal width of the alveolar crest just before implant placement).
Again, the patients were instructed to take antibiotics (amoxicillin, 1,000 mg or clindamycin, 300 mg three times a day) and ibuprofen 400 mg to prevent inflammation and swelling 1 hour before implant placement. Ibuprofen was continued for 3 days and the antibiotics for 6 days postaugmentation. Immediately prior to surgery, a mouth rinse with 0.2% chlorhexidine solution for 3 minutes was performed. A palatal shifted crestal incision in the maxilla or a central crestal incision in the mandible was followed by a sulcular incision at the adjacent tooth without a relieving incision. Orally and buccally, full-thickness flaps were elevated to allow for evaluation of the site, followed by subsequent split-flap preparation to avoid denudating the transplanted bone. The microscrews were removed using stab
incisions through the periosteum. Again, the width of the alveolar crest was measured with a caliper at the central position of the planned implant and recorded. The implants (Screwline Promote Plus, Camlog) were placed with the positioning guide (Figs 9 and 12). In addition, a connective tissue graft, harvested from the hard palate, was placed in the anterior regions. The soft tissue grafts were placed buccally and occlusally to thicken the soft tissue. Wound closure was accomplished with a combination of deep horizontal mattress and interrupted sutures (Trofilene 6-0, Stoma). The single sutures were removed on day 8, the mattress sutures on day 14 after surgery. Again, attention was paid to avoid any pressure from the RDPs on the soft tissue during the healing period of the implant.
The implants were uncovered after a mean healing period of 3.1 (± 0.3) months in the mandible and after 5.2 (± 0.9) months in the maxilla. This study focused on soft tissue and bone graft healing as well as on the stability and amount of resorption of the bone grafts. Differences in the width of the alveolar crest before grafting, just after grafting, and after consolidation of the bone grafts were measured and evaluated. The data were imported into a statistics program (SPSS, IBM) and evaluated. The data were examined using the Kolmogorov-Smirnov test for a normal distribution. For comparisons of the amount of resorption after healing, a Student t test was performed. For comparison of the gain of augmented bone, the one-sample t test was performed.
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273
Fig 10 Severe horizontal bony defect. Bone shell fixed at the buccal alveolar crest with a titanium microscrew.
Fig 11 Grafting of the bony defect between the shell and the alveolar crest with autogenous bone chips mixed with blood.
Fig 12 Reentry 5 months postaugmentation with good integration of the bone graft and reconstruction of the alveolar crest.
Results
cause of a distinct overcontouring of the alveolar ridge. The mean width of the alveolar crest preoperatively amounted to 2.7 mm (± 0.9). After bone grafting, the mean width amounted to 6.7 mm (± 0.8) and was 5.9 mm (± 0.7) at the time of implant placement. The mean gain of the width of the alveolar crest from presurgery to implant placement was 3.3 mm (± 0.9), which equates to a horizontal widening of the crest of 2.5 mm (± 1.0) (P < .001; onesample t test). The mean resorption of the bone graft from the augmentation procedure to implant placement (consolidation of the bone graft) was 0.8 mm (± 0.5) (P < .001; paired t test). This represented a resorption of the graft of 19% (± 13%). All data were normally distributed (Kolmogorov-Smirnov test).
After a mean healing period of 5.5 (± 1.0) months, all 42 implants were installed in the previously planned positions. No implant was lost during the healing period. Cases, regions of augmentation, width of the alveolar crest before grafting, after grafting, and before implant placement, bone gains, and resorption are shown in Table 1.
Between March 2009 and April 2011, 22 patients (11 women, 11 men) underwent implant treatment with a total of 42 implants combined with a two-stage ridge augmentation with a modified shell technique. The mean age was 51.7 (± 15.8) years for women and 43.5 (± 13.4) years for men. Thirty cases were performed to augment 50 horizontal regions with a two-stage procedure. The augmented regions where no implants were placed were planned as a pontic area between implants and were restored with fixed dental prostheses. In one case, a wound dehiscence during bone healing was observed. The resorption of the graft amounted to 44%. Nevertheless, the placement of an implant in the planned position was possible be-
Discussion Horizontal hard tissue augmentation using the technique described resulted in a predictable reconstruction of the bony alveolar ridge. All implants could be placed in their previously planned positions, so the working hypotheses could be accepted. Since introduction of guided bone regeneration in 1990,2,3 many
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274
Table 1 Individual measurements of all augmented regions, resorption of the graft, and gain of the width of the crest Patient no. 1 2
3 4
5 6 7 8 9 10 11 12 13 14
15 16 17 18 19 20 21 22
Mean ± SD
Region* 9 19 21 29 31 19 20 30 23 24 26 26 8 19 7 8 9 8 18 17 16 7 20 19 8 8 19 20 21 28 29 30 29 30 9 9 13 14 19 20 6 8 11 6 7 10 23 24 25 26
Preoperative HW (mm) 3.5 2.0 2.5 2.0 2.5 3.0 2.0 3.5 4.5 2.5 1.0 4.0 1.5 4.0 2.5 1.0 2.0 3.5 3.5 3.0 3.0 2.0 4.5 3.0 4.5 3.5 2.5 3.0 3.5 3.5 3.0 3.0 2.0 2.0 3.0 3.0 3.5 2.5 1.5 2.0 2.5 2.5 2.5 1.5 2.0 2.0 3.5 1.5 1.5 2.5 2.7 ± 0.9
Postaugmentation Pre-implant HW (mm) HW (mm) 7.5 6.5 6.0 5.5 5.5 5.0 5.5 5.0 6.0 5.5 7.0 6.5 7.0 6.0 7.0 6.5 8.0 6.0 7.0 5.5 7.0 5.5 8.0 6.0 7.5 7 7.5 7.0 6.0 5.5 7.5 6.0 7.0 6.0 8.0 6.0 8.0 6.5 7.0 6.5 6.5 6.0 6.0 4.0 6.5 6.0 7.0 6.0 8.5 8.0 8.0 7.5 6.5 7.5 6.0 6.5 5.0 5.5 5.0 6.0 5.5 6.5 6.5 7.0 6.0 5.5 6.5 6.0 7.0 6.5 7.5 6.5 7.0 6.0 6.5 6.5 6.5 6.5 6.5 6.5 6.0 6.5 6.0 6.0 7.5 7.0 5.5 6.0 5.0 6.0 5.5 5.0 6.0 6.5 4.5 5.5 5.0 4.5 6.0 6.0 6.7 ± 0.8
5.9 ± 0.7
Resorption (mm) 1.0 0.5 0.5 0.5 0.5 0.5 1.0 0.5 2.0 1.5 1.5 2.0 0.5 0.5 0.5 1.5 1.0 2.0 1.5 0.5 0.5 2.0 0.5 1.0 0.5 0.5 1.0 0.5 0.5 1.0 1.0 0.5 0.5 0.5 0.5 1.0 1.0 0.0 0.0 0.0 0.5 0.0 0.5 0.5 1.0 0.5 0.5 1.0 0.5 0.0
Resorption (%) 25 13 17 14 14 13 2 14 57 33 25 50 8 14 14 23 20 44 33 13 14 50 25 25 13 11 20 14 25 40 29 13 13 11 13 22 29 0 0 0 13 0 10 11 25 14 17 25 14 0
Gain (mm) 3.0 3.5 2.5 3.0 3.0 3.5 4.0 3.0 1.5 3.0 4.5 2.0 5.5 3.0 3.0 5.0 4.0 2.5 3.0 3.5 3.0 2.0 1.5 3.0 3.5 4.0 4.0 3.0 1.5 1.5 2.5 3.5 3.5 4.0 3.5 3.5 2.5 4.0 5.0 4.5 3.5 3.5 4.5 4.0 3.0 3.0 2.5 3.0 3.0 3.5
Gain (%) 186 275 200 250 220 217 300 186 133 220 550 150 467 175 220 600 300 171 186 217 200 200 133 200 178 214 260 200 143 143 183 217 275 300 217 217 171 260 433 325 240 240 280 367 250 250 171 300 300 240
0.8 ± 0.5
19 ± 13
3.3 ± 0.9
246 ± 97
HW = horizontal width of the alveolar crest. *Universal tooth-numbering system.
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275 different techniques for horizontal ridge augmentation have been described. Today, many questions are still open and the topic is controversial. Are bone substitutes as good as or even better than autogenous bone? Is a membrane necessary for successful bone grafting? If yes, is a resorbable membrane as good as a nonresorbable membrane? Are bone splitting and spreading techniques more effective than additive grafting techniques?6,9,21 To prevent exposed microstructured implant shoulders, representing esthetic and functional failures of implant-supported reconstructions and also the possibility for peri-implantitis,22 a stable bone layer of a minimum width of 2 mm around a dental implant is necessary.23 Guided bone regeneration procedures with bone substitutes for horizontal augmentation should be combined with nonresorbable expanded polytetrafluoroethylene membranes. However, the risk of wound dehiscence and infection with these membranes is higher compared with procedures with resorbable collagen membranes.24 Therefore, for horizontal grafting of narrow ridges, where the host bone is less than 3.5 mm in width, autogenous bone blocks without membranes should be used.25 Covering these bone blocks with nonresorbable membranes reduced resorption.26 Resorptions of autogenous grafts from 30% to 60% were reported, if no covering membranes were used.5 Maiorana et al showed that the resorption of bone blocks was
reduced from 18.3% to 9.3% when covered with bovine bone substitute.27 von Arx and Buser covered the bone blocks with organic bovine bone mineral and a resorbable membrane. The resorption of the graft at reentry was only 0.36 mm, and the resorbable membrane did not cause wound infection.24 Cordaro et al reported resorption of horizontal augmented bone blocks up to 1.2 mm, which related to 22%.28 Their data are very close to the results presented in this study. These data showed that a resorption of horizontal augmented bone grafts of about 1 mm is found in daily clinical practice. Therefore, it is necessary to overcontour the augmented region with hard tissue or to compensate the buccal defect by thickening the soft tissue with connective tissue grafts.29 The major advantage of the shell technique in comparison with a simple bone block augmentation placed as an inlay graft is the regeneration of vital bone.18,19 The shells of about 1-mm thickness serve as a barrier to prevent soft tissue ingrowths and resorption of the bone chips and provide the shape of the graft. The blood supply from the host bone allows nutrition for the survival of the bone chips. Normal bleeding during drilling of the implant bed was observed in all 42 cases and indicated vital bone cells. The modified technique described above is less technique sensitive compared with intraoral harvesting and extraoral trimming of the bone shells with the cutting
wheel, as described by Khoury et and Khoury.18,19 Thinning the thick bone block with the bone mill is very comfortable, and the thickness can be easily controlled.20 Additionally, the shape of the bone shell is slightly convex such as the alveolar crest according to the circular rasp of the bone mill. Another advantage is the simultaneous harvesting of the particulate bone chips by thinning the bone block. Hence, only one donor site is necessary. Future clinical studies are needed to histologically evaluate the vitality of the regenerated bone and the long-term survival rate of the inserted implants.
Conclusions Within the limitations of this case series, the modified shell technique provided a reliable horizontal reconstruction of the alveolar crest with vital bone. This technique allowed for the reconstruction of critical-sized defects of the alveolar crest with intraorally harvested autogenous bone. However, a mean buccal resorption of 0.8 mm was observed. Overcontouring of the augmented graft of approximately 1 mm is recommended.
Acknowledgments The authors thank Dr Kurt Erdelt for performing the statistical analysis of this study. The authors reported no conflicts of interest related to this study.
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276 References 1. Spiekermann H. Implantology. Color Atlas of Dental Medicine. Suttgart: Thieme, 1995. 2. Buser D, Bragger U, Lang NP, Nyman S. Regeneration and enlargement of jaw bone using guided tissue regeneration. Clin Oral Implants Res 1990;1:22–32. 3. Nyman S, Lang NP, Buser D, Bragger U. Bone regeneration adjacent to titanium dental implants using guided tissue regeneration: A report of two cases. Int J Oral Maxillofac Implants 1990;5:9–14. 4. Buser D, Dula K, Belser U, Hirt HP, Berthold H. Localized ridge augmentation using guided bone regeneration. 1. Surgical procedure in the maxilla. Int J Periodontics Restorative Dent 1993;13: 29–45. 5. Buser D, Dula K, Belser UC, Hirt HP, Berthold H. Localized ridge augmentation using guided bone regeneration. II. Surgical procedure in the mandible. Int J Periodontics Restorative Dent 1995; 15:10–29. 6. Chiapasco M, Zaniboni M, Boisco M. Augmentation procedures for the rehabilitation of deficient edentulous ridges with oral implants. Clin Oral Implants Res 2006;17(suppl 2):136–159. 7. Chiapasco M, Casentini P, Zaniboni M. Bone augmentation procedures in implant dentistry. Int J Oral Maxillofac Implants 2009;24(suppl):237–259. 8. Jensen SS, Terheyden H. Bone augmentation procedures in localized defects in the alveolar ridge: Clinical results with different bone grafts and bone-substitute materials. Int J Oral Maxillofac Implants 2009;24(suppl):218–236. 9. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants 2007;22:49–70. 10. Block MS, Degen M. Horizontal ridge augmentation using human mineralized particulate bone: Preliminary results. J Oral Maxillofac Surg 2004;62:67–72. 11. Moghadam HG. Vertical and horizontal bone augmentation with the intraoral autogenous J-graft. Implant Dent 2009;18:230–238.
12. Merli M, Migani M, Esposito M. Vertical ridge augmentation with autogenous bone grafts: Resorbable barriers supported by ostheosynthesis plates versus titanium-reinforced barriers. A preliminary report of a blinded, randomized controlled clinical trial. Int J Oral Maxillofac Implants 2007;22:373–382. 13. Roccuzzo M, Ramieri G, Bunino M, Berrone S. Autogenous bone graft alone or associated with titanium mesh for vertical alveolar ridge augmentation: A controlled clinical trial. Clin Oral Implants Res 2007;18:286–294. 14. Block MS, Baughman DG. Reconstruction of severe anterior maxillary defects using distraction osteogenesis, bone grafts, and implants. J Oral Maxillofac Surg 2005;63:291–297. 15. Felice P, Pistilli R, Lizio G, Pellegrino G, Nisii A, Marchetti C. Inlay versus onlay iliac bone grafting in atrophic posterior mandible: A prospective controlled clinical trial for the comparison of two techniques. Clin Implant Dent Relat Res 2009;11(suppl 1):e69–e82. 16. van der Meij EH, Blankestijn J, Berns RM, et al. The combined use of two endosteal implants and iliac crest onlay grafts in the severely atrophic mandible by a modified surgical approach. Int J Oral Maxillofac Surg 2005;34:152–157. 17. Pikos MA. Block autografts for localized ridge augmentation: Part II. The posterior mandible. Implant Dent 2000;9:67– 75. 18. Khoury F, Khoury CH. Mandibular bone block grafts: Instrumentation, harvesting technique and application. J Par Implant Oral 2006;25:15–34. 19. Khoury F, Khoury CH. Mandibular bone block grafts: Diagnosis, instrumentation, harvesting techniques and surgical procedures. In: Khoury F, Antoun, H, Missika P (eds). Bone Augmentation in Oral Implantology. London: Quintessence, 2007. 20. Stimmelmayr M, Güth JF, Schlee M, Göhring TN, Beuer F. Use of a modified shell technique for three-dimensional bone grafting: Description of a technique. Aust Dent J 2012;57:93–97.
21. Esposito MG, Coulthard P, Worthington HV. How effective is bone augmentation in implant treatment. Int J Oral Maxillofac Implants 2006;21:696–710. 22. Schwarz F, Sahm N, Schwarz K, Becker J. Impact of defect configuration on the clinical outcome following surgical regenerative therapy of peri-implantitis. J Clin Periodontol 2010;37:449–455. 23. Ishikawa T, Salama M, Funato A, et al. Three-dimensional bone and soft tissue requirements for optimizing esthetic results in compromised cases with multiple implants. Int J Periodontics Restorative Dent 2010;30:503–511. 24. von Arx T, Buser D. Horizontal ridge augmentation using autogenous block grafts and the guided bone regeneration technique with collagen membranes: A clinical study with 42 patients. Clin Oral Implants Res 2006;17:359–366. 25. Chiapasco M, Abati S, Romeo E, Vogel G. Clinical outcome of autogenous bone blocks or guided bone regeneration with e-PTFE membranes for the reconstruction of narrow edentulous ridges. Clin Oral Implants Res 1999;10:278–288. 26. Antoun H, Sitbon JM, Martinez H, Missika P. A prospective randomized study comparing two techniques of bone augmentation: Onlay graft alone or associated with a membrane. Clin Oral Implants Res 2001;12:632–639. 27. Maiorana C, Beretta M, Salina S, Santoro F. Reduction of autogenous bone graft resorption by means of bio-oss coverage: A prospective study. Int J Periodontics Restorative Dent 2005;25:19–25. 28. Cordaro L, Torsello F, Accorsi Ribeiro C, Liberatore M, Mirisola di Torresanto V. Inlay-onlay grafting for three-dimensional reconstruction of the posterior atrophic maxilla with mandibular bone. Int J Oral Maxillofac Surg 2010;39:350–357. 29. Grunder U, Gracis S, Capelli M. Influence of the 3-D bone-to-implant relationship on esthetics. Int J Periodontics Restorative Dent 2005;25:113–119.
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269
Two-Stage Horizontal Bone Grafting with the Modified Shell Technique for Subsequent Implant Placement: A Case Series
Michael Stimmelmayr, Priv Doz Dr Med Dent1 Wolfgang Gernet, Prof Dr Med Dent Dr hc, PhD2 Daniel Edelhoff, Prof Dr Med Dent, PhD2 Jan-Frederik Güth, Dr Med Dent3 Arndt Happe, Priv Doz Dr Med Dent4 Florian Beuer, Priv Doz Dr Med Dent, PhD2 This case series evaluated the graft stability and resorption of a modified shell technique for horizontal ridge augmentation. Autogenous bone shells of 1-mm thickness were fixed with microtitanium screws with the gaps between the shells and ridge filled with autogenous bone chips. In 22 patients, 30 cases were performed to augment 50 regions. Forty-two implants were inserted after a healing period of 5.5 (± 1.0) months. Preoperatively, the mean width of the crest was 2.7 mm (± 0.9), after bone grafting, 6.7 mm (± 0.8), and during implant placement, 5.9 mm (±0.7), and the mean resorption was 0.8 mm (± 0.5) (P < .001). This technique showed promising results. However, due to slight resorption, the ridge should be over contoured. (Int J Periodontics Restorative Dent 2014;34:269–276. doi: 10.11607/prd.1374)
Assistant Professor, Department of Prosthodontics, University of Munich, Munich, Germany, and Private Practice, Cham, Germany. 2Tenured Professor, Department of Prosthodontics, University of Munich, Munich, Germany. 3Assistant Professor, Department of Prosthodontics, University of Munich, Munich, Germany. 4Assistant Professor, Department of Oral and Maxillofacial Plastic Surgery and Implantology, University of Cologne, Cologne, Germany. 1
Correspondence to: Dr Michael Stimmelmayr, Josef-Heilingbrunnerstr.2, 93413 Cham, Germany; fax: 09971 843588; email: [email protected]. ©2014 by Quintessence Publishing Co Inc.
While an inadequate horizontal bone width of the alveolar crest was an absolute contraindication for implant placement in the late 1980s,1 guided bone regeneration substantially expanded the range of indications for dental implants in the early 1990s.2,3 Initially, tenting screws and membranes were used to provide space for regeneration4; however, bone substitutes or bone grafts showed better clinical results.5 Small horizontal defects can be reconstructed very predictably with these techniques.6 However, the predictability of the technique decreases when the size of the defect increases.7–9 It has been shown that there is a critical size for bone defects where they cannot be reconstructed with bone substitutes.10 Hence, reconstruction of such defects increases the need for augmentation with autogenous bone grafts.11–13 But additional bone grafting at reentry is often required.12,14 In the past, autogenous bone of the iliac crest was taken for major horizontal and vertical augmentation procedures. Due to the higher resorption and morbidity
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270 of the donor site, today intraoral donor sites are more popular.15,16 Current concepts involve intraoral bone harvesting from the chin or the retromolar region. Pikos described the inlay technique, which involves placing cortical block grafts to accurately fit the residual alveolar bone.17 However, the mandibular cortical block graft needs a long period of time to become vascularised and remodeled and can be sequestrated years after the augmentation procedure.18 Khoury and Khoury described the shell technique for three-dimensional hard tissue grafting.18,19 This technique uses thin cortical bone shells to reconstruct the buccal plate and provide a space for particulated autogenous bone grafts. In this concept, the thinned cortical bone shells serve as a natural barrier membrane that maintains space and prevents soft tissue ingrowth. Harvesting these bone shells and extraoral trimming with the cutting wheel, as originally described, is very technique sensitive.18,19 Therefore, this technique was simplified by thinning out the corticocancellous bone grafts with a bone mill to create the bone shells.20 This technique was used in this study. It was hypothesized that the horizontal hard tissue augmentation of the alveolar ridge with the modified shell technique and autogenous bone will present a predictable outcome after healing, with moderate resorption and a bone volume that allows for restorativedriven implant placement.
Method and materials The requirements of the Helsinki Declaration were observed, and all patients gave informed consent for the surgical procedures. Patients that presented in the private practice of the corresponding author with partial tooth loss and a demand for rehabilitation with implant-supported fixed dental prostheses were consecutively enrolled in the study. In addition, the horizontal resorption of the alveolar crest at the planned implant position caused a two-stage procedure of hard tissue augmentation and implant placement. The appropriate restorative-driven implant position was determined by a wax-up that was transferred into a surgical guide. The exact implant position was clearly defined by a radio-opaque titanium tube (CT-Tube, Camlog) preaugmentation procedure. Implant planning was followed by a panoramic radiograph (Gendex OrthOralix 9200) and bone mapping using the planning model to evaluate the available host bone. The two-stage procedure was preferred when the position of the implant was outside the contour of the alveolar crest or if primary stability of the implant was not expected. All patients were instructed to take antibiotics (amoxicillin, 1,000 mg or clindamycin, 300 mg, 3 pills), ibuprofen 400 mg, and 50 mg prednisolon (Decortin, Merck-Pharma) to prevent inflammation and swelling 1 hour before ridge augmentation. Ibuprofen was continued for 3 days and the
antibiotics for 6 days postaugmentation. Immediately before surgery, the patients were asked to rinse their mouths with a 0.2% chlorhexidine solution for 3 minutes. A palatal shifted crestal incision in the maxilla or a central crestal incision in the mandible was followed by a sulcular incision at the adjacent tooth with only one distal relieving incision. A full-thickness flap was elevated, and all connective or granulation tissue was debrided from the alveolar crest with a curette (Fig 1). For a tension-free wound closure, the periosteum was slit basal of the flap at the beginning of the surgery to minimize bleeding during placement of the bone graft or membrane. Intraoperatively, the width of the alveolar crest was measured with a caliper (Züricher Modell, Seitz & Haag) at the central position of the planned implant as indicated by the positioning guide. The bony defect was measured with a periodontal probe (PCPNC North Carolina, Stoma) to determine the size of the bone shells. The bone graft was harvested at the oblique line in the retromolar region using an ultrasonic knife (Piezosurgery, Mectron). A corticocancellous block-graft of approximately 3-mm thickness was obtained (Figs 2 to 4). The use of an ultrasonic device seems to be more time consuming in comparison with the use of a fissure bur or diamond disk, but the technique is reported to be very safe and atraumatic. The donor site was filled with a collagen fleece (Resorba) and sutured with a row of single sutures
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271
HW pre-op
Fig 1 Severe horizontal bony defect. (HW pre-op = horizontal width of the alveolar crest before horizontal augmentation).
Figs 2 and 3 Bone block harvesting from the retromolar region with an ultrasonic device.
Fig 4 Bone block of 3-mm thickness harvested from the retromolar area.
Fig 5 Bone block placed in the bone mill during the milling process.
Fig 6 Bone block of 1-mm thickness after the milling process.
(Supramid 5-0, Stoma). The block was reduced to a thickness of approximately 1 mm with a bone mill (Bull Bone Mill, Mondeal) (Figs 5 and 6). The advantage of using the bone mill in comparison to a Luer forceps is the consistent abrasion of the bone block, leading to a smooth concave surface of the bone shells. These bone shells were trimmed and adjusted with a round bur and anchored in the host bone with titanium micro screws (Q-Bone-Grafting Set, Trinon) (Figs 7 and 10). The gap between the
shells and the alveolar bone was filled with milled bone chips obtained by thinning the corticocancellous block. Autogenous blood, taken from a vein of the left arm, was added to the graft (Figs 8 and 11). Immediately after the augmentation procedure, the width of the alveolar crest was measured with a caliper at the central position of the planned implant and recorded. The bone graft was covered with a resorbable collagen membrane (Bio-Gide, Geistlich), and the wound was closed with a combination of
deep horizontal mattress (Gore-Tex 6-0, WL Gore) and interrupted sutures (Trofilene 6-0, Stoma). The single sutures on the retromolar donor site and on the grafted site were removed on day 10, the mattress sutures on day 14 after surgery. Attention was meticulously paid to avoid any pressure from the removable dental prostheses (RDPs) on the graft during the healing period. The implants were placed after a mean healing period of 5.5 (± 1.0) months after augmentation.
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272
HW postaug HW pre-impl
Fig 7 Bone shells fixed at the buccal alveolar crest with titanium microscrews.
Fig 8 Grafting of the bony defect between the shells and the alveolar crest with autogenous bone chips mixed with blood (HW postaug = horizontal width of the alveolar crest just after horizontal augmentation).
Fig 9 Reentry and implant placement 5 months postaugmentation with good integration of the bone graft and reconstruction of the alveolar crest (HW pre-impl = horizontal width of the alveolar crest just before implant placement).
Again, the patients were instructed to take antibiotics (amoxicillin, 1,000 mg or clindamycin, 300 mg three times a day) and ibuprofen 400 mg to prevent inflammation and swelling 1 hour before implant placement. Ibuprofen was continued for 3 days and the antibiotics for 6 days postaugmentation. Immediately prior to surgery, a mouth rinse with 0.2% chlorhexidine solution for 3 minutes was performed. A palatal shifted crestal incision in the maxilla or a central crestal incision in the mandible was followed by a sulcular incision at the adjacent tooth without a relieving incision. Orally and buccally, full-thickness flaps were elevated to allow for evaluation of the site, followed by subsequent split-flap preparation to avoid denudating the transplanted bone. The microscrews were removed using stab
incisions through the periosteum. Again, the width of the alveolar crest was measured with a caliper at the central position of the planned implant and recorded. The implants (Screwline Promote Plus, Camlog) were placed with the positioning guide (Figs 9 and 12). In addition, a connective tissue graft, harvested from the hard palate, was placed in the anterior regions. The soft tissue grafts were placed buccally and occlusally to thicken the soft tissue. Wound closure was accomplished with a combination of deep horizontal mattress and interrupted sutures (Trofilene 6-0, Stoma). The single sutures were removed on day 8, the mattress sutures on day 14 after surgery. Again, attention was paid to avoid any pressure from the RDPs on the soft tissue during the healing period of the implant.
The implants were uncovered after a mean healing period of 3.1 (± 0.3) months in the mandible and after 5.2 (± 0.9) months in the maxilla. This study focused on soft tissue and bone graft healing as well as on the stability and amount of resorption of the bone grafts. Differences in the width of the alveolar crest before grafting, just after grafting, and after consolidation of the bone grafts were measured and evaluated. The data were imported into a statistics program (SPSS, IBM) and evaluated. The data were examined using the Kolmogorov-Smirnov test for a normal distribution. For comparisons of the amount of resorption after healing, a Student t test was performed. For comparison of the gain of augmented bone, the one-sample t test was performed.
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273
Fig 10 Severe horizontal bony defect. Bone shell fixed at the buccal alveolar crest with a titanium microscrew.
Fig 11 Grafting of the bony defect between the shell and the alveolar crest with autogenous bone chips mixed with blood.
Fig 12 Reentry 5 months postaugmentation with good integration of the bone graft and reconstruction of the alveolar crest.
Results
cause of a distinct overcontouring of the alveolar ridge. The mean width of the alveolar crest preoperatively amounted to 2.7 mm (± 0.9). After bone grafting, the mean width amounted to 6.7 mm (± 0.8) and was 5.9 mm (± 0.7) at the time of implant placement. The mean gain of the width of the alveolar crest from presurgery to implant placement was 3.3 mm (± 0.9), which equates to a horizontal widening of the crest of 2.5 mm (± 1.0) (P < .001; onesample t test). The mean resorption of the bone graft from the augmentation procedure to implant placement (consolidation of the bone graft) was 0.8 mm (± 0.5) (P < .001; paired t test). This represented a resorption of the graft of 19% (± 13%). All data were normally distributed (Kolmogorov-Smirnov test).
After a mean healing period of 5.5 (± 1.0) months, all 42 implants were installed in the previously planned positions. No implant was lost during the healing period. Cases, regions of augmentation, width of the alveolar crest before grafting, after grafting, and before implant placement, bone gains, and resorption are shown in Table 1.
Between March 2009 and April 2011, 22 patients (11 women, 11 men) underwent implant treatment with a total of 42 implants combined with a two-stage ridge augmentation with a modified shell technique. The mean age was 51.7 (± 15.8) years for women and 43.5 (± 13.4) years for men. Thirty cases were performed to augment 50 horizontal regions with a two-stage procedure. The augmented regions where no implants were placed were planned as a pontic area between implants and were restored with fixed dental prostheses. In one case, a wound dehiscence during bone healing was observed. The resorption of the graft amounted to 44%. Nevertheless, the placement of an implant in the planned position was possible be-
Discussion Horizontal hard tissue augmentation using the technique described resulted in a predictable reconstruction of the bony alveolar ridge. All implants could be placed in their previously planned positions, so the working hypotheses could be accepted. Since introduction of guided bone regeneration in 1990,2,3 many
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274
Table 1 Individual measurements of all augmented regions, resorption of the graft, and gain of the width of the crest Patient no. 1 2
3 4
5 6 7 8 9 10 11 12 13 14
15 16 17 18 19 20 21 22
Mean ± SD
Region* 9 19 21 29 31 19 20 30 23 24 26 26 8 19 7 8 9 8 18 17 16 7 20 19 8 8 19 20 21 28 29 30 29 30 9 9 13 14 19 20 6 8 11 6 7 10 23 24 25 26
Preoperative HW (mm) 3.5 2.0 2.5 2.0 2.5 3.0 2.0 3.5 4.5 2.5 1.0 4.0 1.5 4.0 2.5 1.0 2.0 3.5 3.5 3.0 3.0 2.0 4.5 3.0 4.5 3.5 2.5 3.0 3.5 3.5 3.0 3.0 2.0 2.0 3.0 3.0 3.5 2.5 1.5 2.0 2.5 2.5 2.5 1.5 2.0 2.0 3.5 1.5 1.5 2.5 2.7 ± 0.9
Postaugmentation Pre-implant HW (mm) HW (mm) 7.5 6.5 6.0 5.5 5.5 5.0 5.5 5.0 6.0 5.5 7.0 6.5 7.0 6.0 7.0 6.5 8.0 6.0 7.0 5.5 7.0 5.5 8.0 6.0 7.5 7 7.5 7.0 6.0 5.5 7.5 6.0 7.0 6.0 8.0 6.0 8.0 6.5 7.0 6.5 6.5 6.0 6.0 4.0 6.5 6.0 7.0 6.0 8.5 8.0 8.0 7.5 6.5 7.5 6.0 6.5 5.0 5.5 5.0 6.0 5.5 6.5 6.5 7.0 6.0 5.5 6.5 6.0 7.0 6.5 7.5 6.5 7.0 6.0 6.5 6.5 6.5 6.5 6.5 6.5 6.0 6.5 6.0 6.0 7.5 7.0 5.5 6.0 5.0 6.0 5.5 5.0 6.0 6.5 4.5 5.5 5.0 4.5 6.0 6.0 6.7 ± 0.8
5.9 ± 0.7
Resorption (mm) 1.0 0.5 0.5 0.5 0.5 0.5 1.0 0.5 2.0 1.5 1.5 2.0 0.5 0.5 0.5 1.5 1.0 2.0 1.5 0.5 0.5 2.0 0.5 1.0 0.5 0.5 1.0 0.5 0.5 1.0 1.0 0.5 0.5 0.5 0.5 1.0 1.0 0.0 0.0 0.0 0.5 0.0 0.5 0.5 1.0 0.5 0.5 1.0 0.5 0.0
Resorption (%) 25 13 17 14 14 13 2 14 57 33 25 50 8 14 14 23 20 44 33 13 14 50 25 25 13 11 20 14 25 40 29 13 13 11 13 22 29 0 0 0 13 0 10 11 25 14 17 25 14 0
Gain (mm) 3.0 3.5 2.5 3.0 3.0 3.5 4.0 3.0 1.5 3.0 4.5 2.0 5.5 3.0 3.0 5.0 4.0 2.5 3.0 3.5 3.0 2.0 1.5 3.0 3.5 4.0 4.0 3.0 1.5 1.5 2.5 3.5 3.5 4.0 3.5 3.5 2.5 4.0 5.0 4.5 3.5 3.5 4.5 4.0 3.0 3.0 2.5 3.0 3.0 3.5
Gain (%) 186 275 200 250 220 217 300 186 133 220 550 150 467 175 220 600 300 171 186 217 200 200 133 200 178 214 260 200 143 143 183 217 275 300 217 217 171 260 433 325 240 240 280 367 250 250 171 300 300 240
0.8 ± 0.5
19 ± 13
3.3 ± 0.9
246 ± 97
HW = horizontal width of the alveolar crest. *Universal tooth-numbering system.
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275 different techniques for horizontal ridge augmentation have been described. Today, many questions are still open and the topic is controversial. Are bone substitutes as good as or even better than autogenous bone? Is a membrane necessary for successful bone grafting? If yes, is a resorbable membrane as good as a nonresorbable membrane? Are bone splitting and spreading techniques more effective than additive grafting techniques?6,9,21 To prevent exposed microstructured implant shoulders, representing esthetic and functional failures of implant-supported reconstructions and also the possibility for peri-implantitis,22 a stable bone layer of a minimum width of 2 mm around a dental implant is necessary.23 Guided bone regeneration procedures with bone substitutes for horizontal augmentation should be combined with nonresorbable expanded polytetrafluoroethylene membranes. However, the risk of wound dehiscence and infection with these membranes is higher compared with procedures with resorbable collagen membranes.24 Therefore, for horizontal grafting of narrow ridges, where the host bone is less than 3.5 mm in width, autogenous bone blocks without membranes should be used.25 Covering these bone blocks with nonresorbable membranes reduced resorption.26 Resorptions of autogenous grafts from 30% to 60% were reported, if no covering membranes were used.5 Maiorana et al showed that the resorption of bone blocks was
reduced from 18.3% to 9.3% when covered with bovine bone substitute.27 von Arx and Buser covered the bone blocks with organic bovine bone mineral and a resorbable membrane. The resorption of the graft at reentry was only 0.36 mm, and the resorbable membrane did not cause wound infection.24 Cordaro et al reported resorption of horizontal augmented bone blocks up to 1.2 mm, which related to 22%.28 Their data are very close to the results presented in this study. These data showed that a resorption of horizontal augmented bone grafts of about 1 mm is found in daily clinical practice. Therefore, it is necessary to overcontour the augmented region with hard tissue or to compensate the buccal defect by thickening the soft tissue with connective tissue grafts.29 The major advantage of the shell technique in comparison with a simple bone block augmentation placed as an inlay graft is the regeneration of vital bone.18,19 The shells of about 1-mm thickness serve as a barrier to prevent soft tissue ingrowths and resorption of the bone chips and provide the shape of the graft. The blood supply from the host bone allows nutrition for the survival of the bone chips. Normal bleeding during drilling of the implant bed was observed in all 42 cases and indicated vital bone cells. The modified technique described above is less technique sensitive compared with intraoral harvesting and extraoral trimming of the bone shells with the cutting
wheel, as described by Khoury et and Khoury.18,19 Thinning the thick bone block with the bone mill is very comfortable, and the thickness can be easily controlled.20 Additionally, the shape of the bone shell is slightly convex such as the alveolar crest according to the circular rasp of the bone mill. Another advantage is the simultaneous harvesting of the particulate bone chips by thinning the bone block. Hence, only one donor site is necessary. Future clinical studies are needed to histologically evaluate the vitality of the regenerated bone and the long-term survival rate of the inserted implants.
Conclusions Within the limitations of this case series, the modified shell technique provided a reliable horizontal reconstruction of the alveolar crest with vital bone. This technique allowed for the reconstruction of critical-sized defects of the alveolar crest with intraorally harvested autogenous bone. However, a mean buccal resorption of 0.8 mm was observed. Overcontouring of the augmented graft of approximately 1 mm is recommended.
Acknowledgments The authors thank Dr Kurt Erdelt for performing the statistical analysis of this study. The authors reported no conflicts of interest related to this study.
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276 References 1. Spiekermann H. Implantology. Color Atlas of Dental Medicine. Suttgart: Thieme, 1995. 2. Buser D, Bragger U, Lang NP, Nyman S. Regeneration and enlargement of jaw bone using guided tissue regeneration. Clin Oral Implants Res 1990;1:22–32. 3. Nyman S, Lang NP, Buser D, Bragger U. Bone regeneration adjacent to titanium dental implants using guided tissue regeneration: A report of two cases. Int J Oral Maxillofac Implants 1990;5:9–14. 4. Buser D, Dula K, Belser U, Hirt HP, Berthold H. Localized ridge augmentation using guided bone regeneration. 1. Surgical procedure in the maxilla. Int J Periodontics Restorative Dent 1993;13: 29–45. 5. Buser D, Dula K, Belser UC, Hirt HP, Berthold H. Localized ridge augmentation using guided bone regeneration. II. Surgical procedure in the mandible. Int J Periodontics Restorative Dent 1995; 15:10–29. 6. Chiapasco M, Zaniboni M, Boisco M. Augmentation procedures for the rehabilitation of deficient edentulous ridges with oral implants. Clin Oral Implants Res 2006;17(suppl 2):136–159. 7. Chiapasco M, Casentini P, Zaniboni M. Bone augmentation procedures in implant dentistry. Int J Oral Maxillofac Implants 2009;24(suppl):237–259. 8. Jensen SS, Terheyden H. Bone augmentation procedures in localized defects in the alveolar ridge: Clinical results with different bone grafts and bone-substitute materials. Int J Oral Maxillofac Implants 2009;24(suppl):218–236. 9. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants 2007;22:49–70. 10. Block MS, Degen M. Horizontal ridge augmentation using human mineralized particulate bone: Preliminary results. J Oral Maxillofac Surg 2004;62:67–72. 11. Moghadam HG. Vertical and horizontal bone augmentation with the intraoral autogenous J-graft. Implant Dent 2009;18:230–238.
12. Merli M, Migani M, Esposito M. Vertical ridge augmentation with autogenous bone grafts: Resorbable barriers supported by ostheosynthesis plates versus titanium-reinforced barriers. A preliminary report of a blinded, randomized controlled clinical trial. Int J Oral Maxillofac Implants 2007;22:373–382. 13. Roccuzzo M, Ramieri G, Bunino M, Berrone S. Autogenous bone graft alone or associated with titanium mesh for vertical alveolar ridge augmentation: A controlled clinical trial. Clin Oral Implants Res 2007;18:286–294. 14. Block MS, Baughman DG. Reconstruction of severe anterior maxillary defects using distraction osteogenesis, bone grafts, and implants. J Oral Maxillofac Surg 2005;63:291–297. 15. Felice P, Pistilli R, Lizio G, Pellegrino G, Nisii A, Marchetti C. Inlay versus onlay iliac bone grafting in atrophic posterior mandible: A prospective controlled clinical trial for the comparison of two techniques. Clin Implant Dent Relat Res 2009;11(suppl 1):e69–e82. 16. van der Meij EH, Blankestijn J, Berns RM, et al. The combined use of two endosteal implants and iliac crest onlay grafts in the severely atrophic mandible by a modified surgical approach. Int J Oral Maxillofac Surg 2005;34:152–157. 17. Pikos MA. Block autografts for localized ridge augmentation: Part II. The posterior mandible. Implant Dent 2000;9:67– 75. 18. Khoury F, Khoury CH. Mandibular bone block grafts: Instrumentation, harvesting technique and application. J Par Implant Oral 2006;25:15–34. 19. Khoury F, Khoury CH. Mandibular bone block grafts: Diagnosis, instrumentation, harvesting techniques and surgical procedures. In: Khoury F, Antoun, H, Missika P (eds). Bone Augmentation in Oral Implantology. London: Quintessence, 2007. 20. Stimmelmayr M, Güth JF, Schlee M, Göhring TN, Beuer F. Use of a modified shell technique for three-dimensional bone grafting: Description of a technique. Aust Dent J 2012;57:93–97.
21. Esposito MG, Coulthard P, Worthington HV. How effective is bone augmentation in implant treatment. Int J Oral Maxillofac Implants 2006;21:696–710. 22. Schwarz F, Sahm N, Schwarz K, Becker J. Impact of defect configuration on the clinical outcome following surgical regenerative therapy of peri-implantitis. J Clin Periodontol 2010;37:449–455. 23. Ishikawa T, Salama M, Funato A, et al. Three-dimensional bone and soft tissue requirements for optimizing esthetic results in compromised cases with multiple implants. Int J Periodontics Restorative Dent 2010;30:503–511. 24. von Arx T, Buser D. Horizontal ridge augmentation using autogenous block grafts and the guided bone regeneration technique with collagen membranes: A clinical study with 42 patients. Clin Oral Implants Res 2006;17:359–366. 25. Chiapasco M, Abati S, Romeo E, Vogel G. Clinical outcome of autogenous bone blocks or guided bone regeneration with e-PTFE membranes for the reconstruction of narrow edentulous ridges. Clin Oral Implants Res 1999;10:278–288. 26. Antoun H, Sitbon JM, Martinez H, Missika P. A prospective randomized study comparing two techniques of bone augmentation: Onlay graft alone or associated with a membrane. Clin Oral Implants Res 2001;12:632–639. 27. Maiorana C, Beretta M, Salina S, Santoro F. Reduction of autogenous bone graft resorption by means of bio-oss coverage: A prospective study. Int J Periodontics Restorative Dent 2005;25:19–25. 28. Cordaro L, Torsello F, Accorsi Ribeiro C, Liberatore M, Mirisola di Torresanto V. Inlay-onlay grafting for three-dimensional reconstruction of the posterior atrophic maxilla with mandibular bone. Int J Oral Maxillofac Surg 2010;39:350–357. 29. Grunder U, Gracis S, Capelli M. Influence of the 3-D bone-to-implant relationship on esthetics. Int J Periodontics Restorative Dent 2005;25:113–119.
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